U.S. patent application number 10/119483 was filed with the patent office on 2003-10-16 for protection switching of interface cards in communication system.
This patent application is currently assigned to ADC DSL Systems, Inc.. Invention is credited to Gottlieb, Gary.
Application Number | 20030196135 10/119483 |
Document ID | / |
Family ID | 28789933 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030196135 |
Kind Code |
A1 |
Gottlieb, Gary |
October 16, 2003 |
Protection switching of interface cards in communication system
Abstract
A communication system includes primary and secondary interface
cards. A switching circuit allows both of the interface cards to
selectively communicate over a medium without inducing reflection.
Further, an automatic detection system is provided to allow a
management circuit to identify which interface card is coupled as
the primary or secondary card.
Inventors: |
Gottlieb, Gary; (Irvine,
CA) |
Correspondence
Address: |
Fogg Slifer Polglaze Leffert & Jay, P.A.
P.O. Box 581009
Minneapolis
MN
55458-1009
US
|
Assignee: |
ADC DSL Systems, Inc.
|
Family ID: |
28789933 |
Appl. No.: |
10/119483 |
Filed: |
April 10, 2002 |
Current U.S.
Class: |
714/13 |
Current CPC
Class: |
H04M 3/12 20130101; H04M
3/18 20130101; H04M 2201/38 20130101; H04M 3/005 20130101 |
Class at
Publication: |
714/13 |
International
Class: |
H02H 003/05 |
Claims
1. A communication system comprising: a switch circuit; a primary
interface card couplable to a communication medium connection via
the switch circuit; and a secondary interface card coupled to the
switch circuit, wherein the secondary interface card controls the
switch circuit to decouple the primary interface card from the
communication medium connection and couple the secondary interface
card to the communication medium connection via the switch
circuit.
2. The communication system of claim 1 further comprising a
management card coupled to the primary and secondary cards, wherein
the management card instructs the secondary interface card to
operate the switch circuit to decouple the primary interface
card.
3. The communication system of claim 1 wherein the primary and
secondary cards each include circuitry to output signals that
identify if the card is primary or secondary.
4. The communication system of claim 1 wherein the primary card is
coupled to illuminate a light emitting diode (LED) when the primary
card is operational, wherein the illuminated LED determines a
current load of the primary card.
5. The communication system of claim 4 wherein the secondary card
is coupled to illuminate a light emitting diode and activate a
relay when the secondary card is operational, wherein the
illuminated LED and activated relay determine a current load of the
secondary card.
6. The communication system of claim 5 further comprising a
management card coupled to the primary and secondary cards, wherein
the management card monitors the current loads of the primary and
secondary cards to identify the cards.
7. A communication system comprising: a communication medium; a
switch circuit including a relay; a first interface card coupled to
the communication medium via the switch circuit; a second interface
card coupled to the relay and switch circuit, wherein the second
interface card controls the relay to decouple the first interface
card from the communication medium and couple the second interface
card to the communication medium via the switch circuit; a
management circuit coupled to the first and second interface cards,
wherein the management circuit selectively activates either the
first or second interface card and determines if the first or
second interface card is coupled to the relay.
8. The communication system of claim 7 wherein the management
circuit monitors a current load of the first and second interface
card to determine if the first or second interface card is coupled
to the relay.
9. The communication system of claim 7 wherein the management
circuit activates the second interface card in response to an
operational defect of the first interface card.
10. A communication system comprising: a switch circuit including a
light emitting diode (LED) and a relay; an interface card coupled
to the switch circuit, the interface card comprising, a relay
control circuit coupled to selectively activate the relay, the
relay control circuit is further coupled to illuminate the LED, and
a feedback circuit to monitor a current load of the relay control
circuit and provide output signals; and a management circuit
coupled to the interface card, wherein the management circuit
selectively activates the relay control circuit and monitors the
output signal of the feedback circuit.
11. The communication system of claim 10 wherein the relay control
circuit comprises: a switch transistor coupled to source current to
the LED and relay; an input transistor coupled to selectively
activate the switch transistor; and first and second comparator
circuits coupled to compare a current conducted through the switch
transistor with first and second references, respectively.
12. The communication system of claim 11 wherein the relay control
circuit further comprises a safety circuit to deactivate the switch
transistor if the relay control circuit is shorted.
13. A method of operating a communication system comprising:
installing a primary interface card; installing a secondary
interface card; selectively activating the primary interface card
using a management card; monitoring a current load of the activated
primary interface card; identifying the activated primary interface
card based upon the monitored current load; and storing the
identification information.
14. The method of claim 13 wherein the primary interface card
current load is defined by a current through a light-emitting diode
(LED) coupled to the primary interface card.
15. The method of claim 13 further comprising: selectively
activating the secondary interface card using a management card;
monitoring a current load of the activated secondary interface
card; identifying the activated secondary interface card based upon
the monitored current load; and storing the identification
information.
16. The method of claim 15 wherein the secondary interface card
current load is defined by a current through a light-emitting diode
(LED) and a relay circuit coupled to the secondary interface
card.
17. A method of identifying an interface card comprising:
activating the interface card; comparing a current load of the
interface card to first and second references; identifying the
interface card as either a primary card or a secondary card based
upon the comparison; and storing data indicating the result of the
identification.
18. The method of claim 17 wherein the secondary card operates a
switch relay circuit and has a higher current load than a current
load of the primary card.
19. A method of operating a communication system comprising:
coupling a primary interface card to a communication medium via a
switch; detecting an operational error of the primary card;
decoupling the primary interface card from the communication
medium; and coupling a secondary interface card to the
communication medium via the switch.
20. The method of claim 19 wherein the secondary interface card
controls the switch.
21. The method of claim 19 wherein a management card detects the
operational error of the primary card and instructs the secondary
card to activate the switch to decouple the primary interface card
from the communication medium and couple the secondary interface
card to the communication medium.
22. A communication switch circuit comprising: a primary card
indicator to provide a visual indication when a primary interface
card is operably coupled to the communication switch circuit; a
secondary card indicator to provide a visual indication when a
secondary interface card is operably coupled to the communication
switch circuit; and a switch circuit relay coupled to the secondary
interface card, such that the switch circuit relay selectively
couples either the primary or secondary interface card to a
communication medium connection in response to a signal from the
secondary interface card.
23. The communication switch circuit of claim 22 wherein the
primary and secondary card indicators are light emitting diodes
(LEDs).
24. A communication interface card comprising: a relay control
circuitry to provide an output signal to a communication switch
circuit; and a feedback circuit coupled to the communication switch
circuit to monitor a load current of the communication interface
card through the communication switch circuit.
25. The communication interface card of claim 24 wherein the relay
control circuitry comprises: a switch transistor to couple a
voltage source to an output node to provide the output signal; and
an input transistor coupled to activate the switch transistor in
response to an externally provided activation signal.
26. The communication interface card of claim 24 wherein the
feedback circuit comprises: a current sensor resistor coupled to an
input node; a first comparator to compare a voltage drop across the
current sensor resistor with a first reference voltage; and a
second comparator to compare the voltage drop across the current
sensor resistor with a second reference voltage.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to communication
systems and in particular the present invention relates to
interface card for communication systems.
BACKGROUND OF THE INVENTION
[0002] Communication system often contains two interface cards to
provide transceiver functions over a medium, such as a coaxial
cable. The two cards include a primary card 101 and a protection
card 102, see FIG. 1. The primary card 101 contains a medium
control switch 103, which couples/decouples its transceiver to a
communication medium 105. Protection card 102 also contains a
medium control switch 104, which couples/decouples its transceiver
to the telecommunication medium 105. Under normal operating
conditions, the medium control switch 103 is ON and the primary
card is coupled to the communication medium and performs
communication functions. The protection card is in a "hot" standby
mode with its medium control switch 104 turned OFF.
[0003] As soon as a management card has determined a failure on the
primary card, switch 103 is turned OFF and switch 104 is turned ON.
The protection card then takes over communication traffic. The
primary and protection cards are typically located physically
distanced one from another. As such, the communication medium, such
as a coaxial cable, is split into two cables 106 and 107. While
cable 106 is connected to transceiver 101 through switch 103 and is
properly terminated, cable 107 is floating because switch 104 is
OFF. Because cards 101 and 102 are two separate entities, floating
cable 107 must have some length, that causes reflection of signal
back into communication medium 105. This can cause data transfer
errors because the communication signals in the medium 105 get
distorted.
[0004] To reduce reflection to a sustainable level, the maximum
length of the floating cable is limited. This limitation, however,
restricts the design of the interface cards. As bandwidth of the
signal in the cable gets wider, the length of the floating cable
must decrease. Because the floating cable cannot have a zero
length, the data rate of the communication equipment is
limited.
[0005] For the reasons stated above, and for other reasons stated
below which will become apparent to those skilled in the art upon
reading and understanding the present specification, there is a
need in the art for a more flexible interface card for
communication system.
SUMMARY OF THE INVENTION
[0006] The above-mentioned problems with communication system and
other problems are addressed by the present invention and will be
understood by reading and studying the following specification.
[0007] In one embodiment, a communication system comprises a
communication medium, a switch circuit, a primary interface card
coupled to the communication medium via the switch circuit, and a
secondary interface card coupled to the switch circuit. The
secondary interface card controls the switch circuit to decouple
the primary interface card from the communication medium and couple
the secondary interface card to the communication medium via the
switch circuit.
[0008] A communication system comprises a communication medium, a
switch circuit including a relay, a first interface card coupled to
the communication medium via the switch circuit, and a second
interface card coupled to the relay and switch circuit. The second
interface card controls the relay to decouple the first interface
card from the communication medium and couple the second interface
card to the communication medium via the switch circuit. A
management card is coupled to the first and second interface cards
and selectively activates either the first or second interface card
and determines if the first or second interface card is coupled to
the relay.
[0009] A method of operating a communication system comprises
installing a primary interface card, installing a secondary
interface card, selectively activating the primary interface card
using a management card, monitoring a current load of the activated
primary interface card, identifying the activated primary interface
card based upon the monitored current load, and storing the
identification information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a block diagram of a prior art interface card
communication system;
[0011] FIG. 2 is a block diagram of an embodiment of an interface
card communication system of the present invention;
[0012] FIG. 3 is a schematic diagram of circuitry included in an
interface card of an embodiment of the present invention; and
[0013] FIG. 4 illustrates a telecommunication system of an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0014] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings, which
form a part hereof, and in which is shown by way of illustration
specific preferred embodiments in which the inventions may be
practiced. These embodiments are described in sufficient detail to
enable those skilled in the art to practice the invention, and it
is to be understood that other embodiments may be utilized and that
logical, mechanical and electrical changes may be made without
departing from the spirit and scope of the present invention. The
following detailed description is, therefore, not to be taken in a
limiting sense, and the scope of the present invention is defined
only by the claims.
[0015] As explained above, prior communication system (see FIG. 1)
contains two interface cards, the primary 101 and the protection
102. Under normal operating conditions, the primary card is coupled
to communication medium 105 via medium control switch 103. In
response to a detected failure of the primary card, protection card
102 is coupled to medium 105 via medium control switch 104 and
switch 103 is turned OFF. When switch 104 is OFF, cable 107 causes
reflection of signal back into communication medium 105. An
embodiment of the present invention changes the switching structure
of the interface card and medium connections.
[0016] Referring to FIG. 2, an embodiment of the present invention
contains a primary interface card 201, a protection, or secondary,
card 202, a management card 200 and a single medium control switch
206. The primary and secondary cards get selectively coupled to
communication medium 205 connection of the medium control switch
206. It will be appreciated that the communication mediums can be
any electrical or optical medium used for communication, such as
but not limited to coaxial cable and fibre optics.
[0017] Medium control switch 206 includes a switch circuit 210 to
selectively couple medium 205 to cards 201 or 202 through cables
203 or 204. Using one switch allows cables 203 and 204 to be any
length and does not result in reflection on medium 205. Protection
card 202 controls operation of switch 206 by activating a relay
226. Under normal conditions, switch 210 connects medium 205
(position 209) to the primary card 201 through the medium 203. If
management card 200 determines that a failure on the primary card
201 has occurred, the protection card turns switch 210 to position
208 to connect the protection card 202 to medium 205. Medium 205
gets properly terminated either on the primary card 201 under
normal conditions or on the protection card 202 after being
switched to it. The proposed solution eliminates a floating cable
and the limitations on card design associated with it.
[0018] Primary card 201 has output node 303 and input node 304 that
are coupled to a light-emitted diode (LED) 220 and current limiting
resistor 224. When the primary card is activated by an activation
signal at input 306 from the management card, LED 220 is
illuminated. The management card can determine if card 201 or card
202 is coupled as the primary card, as explained in detail below,
by using output nodes 307 and 308.
[0019] The above embodiment of the present invention requires one
medium control switch as opposed to two switches necessary for
prior systems. Typically, cards 201 and 202 are the same by design.
One of them is considered primary and another becomes a protection
card. Each card includes relay control circuitry and feedback
circuitry. Referring to FIG. 3, an embodiment of relay control
circuitry 301 and feedback circuitry 302 is described. Input node
306 receives an activation signal from the management card, and
output nodes 307 and 308 are coupled to provide feedback to the
management card. During an evaluation operation, either during
troubleshooting or at initialization, the management card activates
node 306 (high voltage). Input transistor 404 is connected to node
306 through resistor 409. A current-limiting resistor 408 is
coupled to transistor switch 403. When transistor 404 is activated,
transistor 403 is activated and node 303 is pulled high. Node 303
is coupled to either an LED or an LED and relay. Feedback circuit
302 is used to identify the card as either a primary (LED only) or
a secondary (LED and relay).
[0020] Feedback circuit 302 contains two comparators 506 and 507,
and current sensor resistor 501. First inputs of comparators are
connected to current sensor resistor 501 through a balance resistor
502. Second inputs of comparators are connected to voltage
references, for instance, a resistor divider circuit 503, 504, 505.
If there is no current conducted through resistor 501, a voltage on
the first inputs of the comparators is lower than reference voltage
applied to their second input. As a result, both comparators output
logic ZERO indicating no current through the load connected to 303
and 304. If the card is connected to an LED, the voltage drop
across resistor 501 activates comparator 507, but not comparator
506. If the card is coupled to an LED and the switch relay 226, the
voltage drop across resistor 501 activates comparator 507 and
comparator 506.
[0021] In addition to identifying the primary and secondary cards,
the management card, or external processor, can determine if nodes
303 and 304 are broken or shorted. If there is no connection
between nodes 303 and 304, a voltage across resistor 501 is 0V and
both comparators output logic ZERO. If node 303 is shorted to
either node 304 or ground, then transistor 403 is turned OFF and a
voltage across resistor 501 is also 0V.
[0022] If node 303 is shorted, the current conducted through
resistor 401 provides a voltage drop across resistor 401 that is
sufficient to turn ON safety transistor 402. When transistor 402
turns ON, transistor 403 is partially turned off. Resistor 407
helps to further reduce current through transistor 403. A voltage
drop across resistor 405 is added to the voltage across resistor
401 to turn ON transistor 402 and to turn transistor 403 OFF. As
such, safety transistor 402 turns off transistor 403 when the
current through resistor 401 is above a threshold level.
[0023] Because the management card "doesn't know" which interface
card is connected as a primary or protection, an evaluation
operation is performed by turning transistor 404 ON and monitoring
the feedback. If a low current load is detected, the evaluated card
is determined to be connected as a primary card. If a high current
load is detected, the evaluated card is determined to be connected
as a protection card. When a protection card is detected, the
management card turns transistor 404 OFF immediately to prevent the
switching of relay 226. The management card stores identification
information about the primary and protection status of the cards.
The management card can then inform a technician what equipment
slot contains the primary card and what equipment slot contains the
protection card. The management card can also switch from the
primary to the protection card as soon as a failure on the primary
card has been detected. It will be appreciated by those skilled in
the art with the benefit of the present invention that the
management card can implement any failure/defect monitoring and
identification method without departing from the present
invention.
[0024] FIG. 4 illustrates a communication system of an embodiment
of the present invention. The system includes client locations 420
that are coupled to communicate with remote transceiver stations
430. Transceiver stations 430 operate as relay stations to
coordinate the communication between the clients and a central
station 440. All of the locations are coupled together using one or
more communication media 450. As such, both the remote and central
station can include primary and secondary interface cards, as
described above. For example, the central station 440 has numerous
cards 460 that are coupled to a back plane (not shown) for
communication with the remote stations.
Conclusion
[0025] A communication system has been described that includes
primary and secondary interface cards. A switching circuit allows
both of the interface cards to selectively communicate over a
medium without inducing reflection. Further, an automatic detection
system is provided to allow a management circuit to identify which
interface card is coupled as the primary or secondary card.
[0026] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement, which is calculated to achieve the
same purpose, may be substituted for the specific embodiment shown.
This application is intended to cover any adaptations or variations
of the present invention. Therefore, it is manifestly intended that
this invention be limited only by the claims and the equivalents
thereof.
* * * * *